Electronic organ system



MASTER 056.

y 1969 E. M. JONES 3,443,017

I ELECTRONIC ORGAN SYSTEM Filed Dec. 2, 1965 7 Sheet I of s ll6 Sl4|5|2H119 118 INVENTOR EDuJARD M. JONES BY d [2071.

ATTORNEYS y 1969 E. M. JONES 3,443,017

ELECTRONIC ORGAN SYSTEM Filed Dec. 2, 1965 Sheet 2 of 3 SQUARE UJAVE I65 e f? BL 4 SQUARE OUTPUT op q R R2 "c LUAVE PREVIOUS STAGE 20o OUTPUTD.C. 201- AMPLH IER LLHTH $16.2 VOLTAGE 2 CURRENT 2 emu i DIQZ'SALUTOOTH OUTPUT a & oEo

REFERENCE POTENTIAL 145V F1 fiv 4.1K

M J 311 cge lmo I f (SK 2 310 e4 SQUARE U A ma, 5 321 9M, 3i4 OUT PUTsmee 301 202 c 'sv L 306 9 WWUT INVENTOR EDLUARDMJONES ATTORNEYS ay 6,1969 E. M. JONES 3,443,017

ELECTRONI C ORGAN SYSTEM Filed Dec. 2, 1965 I Sheet 3 of 3 G, +J6v 404 QAOOu-wf 3 H 0 we? SQUARE OUTPQT wAvE OUTPUT OP PREV. STAGE OUTPUT a 5 r1 2 5 4 s *7 7 TV 346 t? V-A W INVENTOR I EDLUARD MJoNEs I ATTORNEYSUnited States Patent 3,443,017 ELECTRONIC ORGAN SYSTEM Edward M. Jones,Cincinnati, Ohio, assignor to D. H. Baldwin Company, Cincinnati, Ohio, acorporation of Ohio Filed Dec. 2, 1965, Ser. No. 511,037 Int. Cl. Gl0h1/00 US. Cl. 84--1.01 12 Claims ABSTRACT OF THE DISCLOSURE An electronicorgan employing an array of nineteen master oscillators from each ofwhich are derived tone signals by means of divide-*by-three circuitsarranged to provide both square and sawtooth waves.

It has heretofore been the usual practice to generate organ tones froman array of twelve master oscillators, by divide-by-two divider chains,so that twelve divider chains are available, each of which providestones of one nomenclature. The tones provided by a divider chain arethen precisely octavely related, and are locked to each other in phase.In order to provide celeste effects, two or more sets of tonegenerators, mutually detuned, are usually utilized.

Where tones are generated by divide-by-three circuits, each chainprovides an array of tones which are of different nomenclature, and thetotal array of tones is such that octavely related tones are notprecisely related in frequency, nor are they locked in phase. Octavesare stretched in frequency, as in a piano. Fifths are out of tune, butnot quite as much as in the tempered state. Twelfths are tuned to zerobeat. By throwing some of the master oscillators sharp and some fiat allthe octaves can be thrown out of tune to desired extents, and rapidbeats can be obtained when various footages are played together, givinga celeste-type effect. This is not a true celeste, as usuallyunderstood, because in the true celeste stops of the same footage areout of tune.

In an organ of the type above described, square waves cannot be obtainedfrom outphased addition of sawtooth waves, nor can sawtooth waves besynchronized by addition of square waves, because all octaves are out oftune. Yet both square wave and sawtooth waveforms are required, toprovide a full complement of tone colors. It is a feature of the presentinvention to provide a divide-bythree organ in which the divide-by-threecircuitry generates both sawtooth and square waveforms, on separateterminals, so that these can be collected by separate key switches, forapplication to separate tone color circuits.

It is a further object of the invention to provide a noveldivide-by-three circuit, directly capable of producing square waves inresponse to square waves, and also capable of providing sawtooth waves.

It is another object of the invention to provide a divideby-threecircuit capable of providing square wave output in response to squarewave input, and which shall utilize a minimum of circuitry composed ofconventional low cost components, in order to minimize cost per divider.

It is a further object of the invention to provide a divide-bythreecircuit responsive to square wave input and providing both square waveand ramp wave output.

Another object of the invention resides in the provision of a squarewave to square wave divide-by-three circuit capable of being tuned by asingle condenser.

While divide-by-three circuits of wide variety can be devised, it isundesirable from a cost viewpoint, that diodes be utilized in producingsawtooth voltages from square wave voltages. It is one feature of theinvention to avoid inclusion of diodes by utilizing the rectifyingeffect available at emitters of semiconductor amplifiers.

A more important feature of the invention involves the provision of adivide-by-three which requires only one tuning capacitor per stage, withpositive lock on of both halves of the divided wave from the input wave,so that dividers operative over the entire gamut of tones can be nearlyidentical, while operation from stage to stage is positively locked.

The above and still further objects, features and advantages of thepresent invention will become apparent upon consideration of thefollowing detailed description of one specific embodiment thereof,especially when taken in conjunction with the accompanying drawings,wherein:

FIGURE 1 is a block diagram of a divide-by-three organ according to theinvention;

FIGURE 2 is a generalized circuit diagram of a divide by-three circuitaccording to the invention, including a high gain amplifier illustratedin block form;

FIGURES 3, 4, 5 are circuit diagrams of amplifiers suitable forinclusion in the circuit of FIGURE 2;

FIGURE 6 is a schematic circuit diagram of a frequency divider accordingto the invention, utilizing two transistors of opposite type;

FIGURE 7 is a schematic circuit diagram of a frequency divider accordingto the invention, utilizing two transistors of the same type; and

FIGURE 8 is a series of plots of waveforms occurring in eachdivide-by-three stage of the invention, and pertaining to FIGURES 2-7,inclusive.

Referring now to FIGURE 1 of the drawings, ninetyseven (97) tone sourcesare illustrated, each in block form, #1 being the source of lowestfrequency and #97 the source of highest frequency. Source #1 is C andsource #97 is C Sources 9779, inclusive, are master oscillators,representing notes C9 to F#7, and provide square wave outputs. Some ofthe sources 97-79, inclusive, are frequently controlled by voltages, +Eand E, supplied at terminals 100, 101. Potentiometers 102, 103 extendfrom terminals 100, 101 to ground, and sliders 104, 105 are connected toceleste control knobs 106. 106 may be a single knob for joint control.Lead 107 extends from slider 104 to sources 80, 83, 88, 91, 94, 97. Lead108 extends from slider 105 to sources 81, 84, 86, 89, 92, 95, asexemplary connections.

What can then be accomplished by knob 106 is to throw some of thesources sharp and some fiat, while some are unaffected, if desired, sothat all the octaves can be thrown selectively or adjustably out oftune. Thereby rapid beats can be obtained when various footages areplayed together, giving a celeste-type effect.

Master oscillator 97 controls a divide-by-three chain including sources78, 59, 40, 21, 2. It will be noted that this chain includes no sourcesof the same nomenclature. Additional divider chains proceed from each ofthe master oscillators, so as to produce the required gamut of tones,from #1 to #97. Obviously, the total number of notes in a given organinvolves a matter of choice. Master oscillators 97-79, inclusive, areprovided only with square wave outputs. Master oscillators 85-79 areprovided with key switches, 110, 111 operated by one key. Key switch 111leads to bus 112, which supplies four-foot sawtooth tone color circuits,while key switch 110 leads to bus 113, which supplies four-foot squarewave tone color circuits. In general, sawtooth tone color filters aresupplied only with sawtooth waves, but in the case of master oscillatornotes, this is not necessary. A third switch not shown would providetwo-foot tones from oscillator 85 from a key an octave below.

Each of the sources #7 8-#1 is provided with two outputs, as 501, 502.Output 501 is a sawtooth signal, which, passing through key switches, as115, leads to sawtooth tone color circuits, as 118, and output 502 is asquare wave signal which, passing through key switches such as 116,leads to square wave tone color circuits, as 119. A typical organ mayinclude 2 square wave, 4 square wave, 8' square wave, 16' square wave,4' sawtooth, 8' sawtooth and 16' sawtooth tone color circuits on two ormore manuals and pedals, so there are many more key switches than areillustrated in FIGURE 1, which only shows key switches for the lowestand highest notes on one manual.

Referring now to FIGURES 2 and 8 of the accom panying drawings, there isillustrated generally a divideby-three circuit which accepts square waveinputs and provides square wave outputs, but which also producessawtooth outputs. The circuit of FIGURE 2 utilizes a DC amplifier Ahaving voltage and current gain very much greater than plus 1, andpreferably of about 100. Such amplifiers, when provided with feedback,can be bistable, i.e., if an input signal is inserted, of sufficientamplitude, feedback drives the amplifier to saturation and holds theamplifier in the condition demanded by the signal. A signal in theopposite sense, then, can overcome the feedback signal and reduce theamplifier to a zero output. The amplifier accordingly has two stablestates, which may be denominated and 1.

Input to the amplifier is supplied from circuit input terminal 200 toamplifier input 201 via differentiating circuit composed of capacitor Cand resistance R The output terminal 202 of the amplifier is thenconnected back to the input terminal via a capacitor C and a resistanceR in series, so that feedback derives from the junction of R and R Aresistance R, is connected directly between input and output. R is notessential, but provides a primary advantage in that it improvestolerances of operation, prevents transfer of state without triggeringaction, and provides stable triggering points. The amplifier may need abias current at its input, assuming transistor amplifier elements, whichis midway between the two currents in R representing the two states ofthe amplifier, and such that the amplifier has a low impedance for onepolarity of signal. A diode D connected between input 201 and areference point provides a low impedance for the other polarity of inputcurrent.

In response to a square wave e triggers are derived by differentiationby C to provide the waveform e As suming that at a given time t thefeedback via C is low, the output of the amplifier will assume thepositive or 1 state, as at t waveform e The amplifier is then maintainedin its 1 state both by feedback via R and via C The next negativetrigger at 1' cannot overcome the two feedbacks, so that the amplifierremains in its 1 state. The trigger e at time t has no effect because itis of the wrong polarity. The current through C has been subsiding, butR holds the amplifier in its 1 state. The next trigger at time 12,, issufficient to overcome the amplifier bias, which now derives primarilyfrom R and the amplifier will transfer to its zero state. Again,feedback via C prevents the next positive trigger, at t fromtransferring state, but at t that feedback has decreased sufiiciently topermit transfer. The result is the generation of waveform e Feedbackfrom the output of the amplifier is differentiated by C to produce avoltage e across R During the negative portion of the cycle the voltagedivider R R produces a voltage e across R in series with D, 2;,approximating a sawtooth of the same frequency as pertains to 6 On theassumption that the amplifier A is transistorized, and for the diode Dpolarity illustrated, it should have low input impedance for negativesignals. If low input exists, instead, for positive signals, diode Dshould be reversed.

Suitable component values for the circuit of FIGURE 2 are, for operationat c.p.s.,

R 1K E volt -.4 R 10K R 22K R 22K C .001 C .12

Suitable configurations of transistors for use in amplifiers A areillustrated in FIGURES 3, 4, 5.

In FIGURE 3, use is made of an NPNP type transistor 220, the [i of thePNP section of the transistor 220 being at least 100. Operation isaccording to the description of FIGURE 2. Positive supply voltage, atterminal 221 is applied via a 1K load resistance 222 for the outputcollector. The input supply voltage is 15 v. applied ".0 terminal 223and resistance 224 of 47K separates the terminal 223 from the inputterminal 225. Waveform e appears at terminal 225 and waveform e.; atterminal 226.

In FIGURE 4 is illustrated an amplifier utilizing an NPN transistor 230connected to drive a PNP transistor 231. The system of FIGURES 2 and 3are therefore analogous. Signal input e is applied to terminal 225, andoutput e derived from terminal 226. Terminal 225 is supplied withnegative bias voltage 15 v. from supply terminal 230 via a resistance224 (47K). Terminal 225 is directly connected to the emitter oftransistor 230, while the base of that transmitter is directly connectedto a reference potential source E which may be slightly below ground, ifdesired. The reference source E is directly connected to the collectorof transistor 231, while the base of transistor 231 is directlyconnected to the collector of transistor 230, output deriving from theemitter of transistor 231. Transistor 231 is thus emitter loaded, and.is provided with a drive signal from transistor 230.

In FIGURE 3, two PNP transistors 240, 241 are employed, each having a 1320. Both transistors 240 and 241 have emitters connected directly toreference voltage E Input signal is applied to the base of transistor240, which has a collector load 242 (10K) connected to a negativeterminal 244 (-15 v.). The collector of transistor 240 is directlyconnected to the base of transistor 241 and the collector of 241 isloaded by resistance 24S (1K). The output terminal 226- derives from thecollector of transistor 241.

The systems of FIGURES 2, 3, 4, 5 employ diodes in order to derivesawtooth waveforms. Instead, the systems of FIGURES 6 and 7 rely on therectifying effect of the emitter of the first transistor of theamplifier A to provide the required sawtooth waveform. The emitterresistor makes the input impedance of this first transistor becomesufliciently high in value not to seriously shunt its base resistor andas a result, the generated sawtooth is, at the base of the transistor,symmetrical. The rectifying action then produces a sawtooth of theproper period, i.e., coextensive with the accompanying square wave fromthe symmetrical sawtooth wave at the base. Further, the system of FIGURE7 has the advantage of utilizing only one type of transistor, althoughspecial biasing is required to keep the first transistor, of the pair oftransistors included in the amplifier, from saturating and having a lowimpedance, and also to provide symmetrical triggering conditions.

The system of FIGURE 6, on the other hand, requires a minimum of supplyand bias voltages, essentially one.

In FIGURE 6, a square wave e may be applied to input terminal 200. Acapacitor 300 (100 /.L/l.f.) and a resistance 301 (47K) are connected inseries with each other and between terminal 300 and the base 302 of theNPN transistor 303, having an emitter 304 and a collector 305. Areference voltage bus 306 is provided, at 0.9 v. although this bus may,in principle, be grounded. A bias resistance 307 (4.7K) is connectedbetween base 302 and bus 306, and a load resistance 308 (4700) isconnected between emitter 304 and bus 306.

The collector 305 is directly connected to the base 310 of a PNPtransistor 311. The emitter 312 of transistor 311 is directly connectedto a positive supply terminal 313, and the collector 314 is connecteddirectly to output terminal 202, a load resistance 315 (1K) beingconnected between output terminal 202 and reference bus 306.

An AC feedback path composed of series capacitor 320 and resistance 321extends between output terminal 202 and base 303. A DC feedback pathcomposed of resistance 322 parallels the AC path, and corresponds infunction and modes of operation to R FIGURE 2, its value being selectedaccording to the principles of the invention explained in describing thecircuit of FIGURE 2.

The operation of the system of FIGURE 6 corresponds with the operationof the system of FIGURE 2, generally, the primary distinction residingin that sawtooth waveform can be derived from emitter 304, i.e., acrossload resistance 308, relying on the rectifying properties of the emitter304. The system'can be tuned by variation of capacitor 320 alone, whichgreatly reduces problems of mass production and tuning of the dividerchains of electric organs.

In FIGURE 6, the impedance of the base-emitter circuit becomessufiiciently high that the resistance 307 is not seriously shunted.Thereby, the input impedance of the system, as seen at input terminal200, and the input impedance, also, as seen by the feedback loops, areessentially the same in both half cycles of the output waveform. Thisimplies that the time constant of the sawtooth wave a (see FIGURE 9) atbase 302, is nearly the same for both half cycles. The pips 340 on eachof waveforms 2 and e derive from differentiation of the input waves.

The bus 306 is maintained at .9 v. to provide a zero DC component forthe sawtooth output, and its value therefore is selected according tothe average value of the DC component. Apart from this consideration,bus 306 could be grounded.

The system of FIGURE 7 corresponds with the system of FIGURE 5, inprinciple, except in that two NPN transistors 400, 401 are employed, andthat sawtooth waveform e;, is derived directly from the emitter oftransistor 400, as in FIGURE 6. Separate bias voltage sources 403, 404are required for the transistors 400, 401, and a considerable number ofdistinct bias sources, to keep transistor 400 operating out ofsaturation, in a high impedance region and to provide symmetricaltriggering conditions for the two half cycles of the signals e Clearly,a wide variety of specific transistor amplifiers can be employed, withinthe broad principles of the invention as indicated in FIGURE 2, whichare defined by the appended claims.

What I claim is:

1. A tone generator for an electric organ,

said tone generator including an array of master oscillators arranged tohave frequencies in accordance with notes of the musical scale andencompassing at least one octave of such notes and having square waveoutput waveforms,

a plurality of divide by three divider chains arranged to provide squarewave output waveforms in response to square wave input waveforms,

each of said divider chains having an input circuit and a plurality offrequency dividers,

means connecting each of said input circuits to one of said masteroscillators,

a plurality of tone forming filters,

key operated means connecting the square wave output waveforms of saidmaster oscillators and of said frequency dividers to selected ones ofsaid tone forming means at will,

an amplifier connected in cascade with said tone forming filters, and

an acoustic radiator driven by said amplifier.

2. The combination according to claim 1 wherein each of said frequencydividers includes means for generating a sawtooth wave ha ving the sameperiod as the square waveform provided by that frequency divider.

3. A divider system, for dividing by an odd integer, including a sourceof square waves, a differentiating circuit responsive to said squarewaves to provide sequential positive and negative pulses,

an amplifier having a large positive amplification factor,

said amplifier having an input terminal connected in series with saiddifferentiating circuit,

said amplifier having an output terminal,

a first feedback circuit extending from said output terminal to saidinput terminal,

a second feedback circuit extending from said output terminal to saidinput terminal,

said first feedback circuit being a feedback circuit capable oftransferring only AC current,

said second feedback circuit being a DC feedback circuit,

said second feedback circuit providing maximum feedback current ofsubstantially smaller value than the maximum current provided by saidfirst feedback circuit in response to said input square wave, said firstfeedback circuit having a time constant appropriate to provide an outputsquare wave having a period equal to an odd integer multiplied by theperiod of said input square waves.

4. The combination according to claim 3, wherein said second feedbackcircuit is arranged to provide approximately one half the current thatis provided by said first feedback circuit in response to said inputsquare waves.

5. The combination according to claim 3, wherein said first feedbackcircuit includes a capacitor and a resistance in series, the timeconstant of said capacitor and resistance being selected to beapproximately equal to half the period of said output square wave.

6. The combination according to claim 3, wherein said odd integer isthree.

7. The combination according to claim 3, wherein is further provided apoint of reference potential, a diode, a load resistance in seriesbetween said input circuit and said point of reference potential, and anoutput terminal connected to the junction of said diode and said loadresistance.

8. The combination according to claim 3, wherein said amplifier includesa first transistor having a base, an emitter and a collector,

means connecting said input circuit to said base,

a point of reference potential,

a load resistance connected between said emitter and said point ofreference potential,

a second transistor,

means connecting said second transistor in driven relation to said firsttransistor, and

means applying operating potentials to said first transistor such thatsaid emitter provides rectification of pulse current tfiow to said loadresistance from said output terminal via said first feedback circuit tosaid base.

9. The combination according to claim 81 wherein said first and secondtransistors are of opposite conductivity types, and wherein a singlesupply voltage is provided for energizing and biasing said transistors.

10. The combination according to claim 8 wherein said transistors are ofthe same conductivity type and are connected in cascade.

11. A divide by three circuit comprising an amplifier having a largepositive gain,

a source of square waves of frequency f,

means differentiating said square waves to provide successive pulse ofalternate polarity,

said amplifier having an input terminal and an output terminal,

means connecting said pulses to said input terminal,

a capactive-resistive feedback circuit between said output terminal andsaid input terminal,

said amplifier and feedback circuit having parameters selected to causetransfer of said amplifier between a first and a second stable stateonly in response to a first of said pulses and thereafter in response toevery third one of said pulses, positive ones of said pulses tending todrive said amplifier into one of said states and negative ones of saidpulses tending to drive said amplifier into the other of said states.

12. The combination according to claim 11 wherein is References CitedUNITED STATES PATENTS 6/1951 Mork 841.19 X 8/1964 Peterson 841.01 X

ARTHUR GAUSS, Primary Examiner.

B. P. DAVIS, Assistant Examiner.

US. Cl. X.R.

